Nova-Tech 2700 Series Benchtop Meters - Manual (Page 48)

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22. DO Electrode Maintenance
Changing the Membrane Cap
The DO 2700 electrode utilizes a cap attached to a pre-installed membrane that
is easily replaced. Replace the membrane cap if it becomes damaged or worn
over time as needed. When calibration can not be completed, look to replace the
electrolyte first as this may help. Replace the membrane cap and electrolyte
together using the following procedure.
1) Unscrew the old membrane cap from the probe. Before installing a new
membrane, clean the probe tip with deionized water to remove any
contaminants.
2) With the membrane cap removed fill it approximately 50% full using the
electrolyte solution. Screw the membrane cap on moderately tight (do not
over-tighten). A small amount of electrolyte should overflow—indicating that
all of the air has been removed.
3) Rinse off excess electrolyte with deionized water.
Electrode Cleaning
Cleaning the BOD probe is only necessary after erratic
readings result; usually after many months of use.
Avoid excessive and un-necessary cleaning, as it can
reduce the life of the probe.
Gold Cathode
The gold cathode can become tarnished or plate with
silver after extended use. It is cleaned with the
adhesive backed sanding disc in the Membrane Kit
provided with the probe. Stick the disc to a flat object,
like a bottle cap, and gently sand the gold cathode with a twisting motion about 3
times or until all silver deposits are removed. The gold will have a matte finish.
Silver Anode
It is normal for a dark layer of silver chloride to cover the silver anode. After
prolonged use it may become necessary to clean the anode. Soak the probe in
14% ammonium hydroxide for 2 to 3 minutes or overnight in a 3% ammonium
hydroxide solution. Rinse with deionized water, recharge the electrode, and install
a new membrane.
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